Is Baking Soda Safe for Plants?
You may have heard that household baking soda can treat plant disease, deter pests, and improve the soil. But is this true? Join farmer Briana Yablonski to learn whether baking soda is safe for plants.
It’s great when we can turn to everyday household items to solve our garden problems. Baking soda is one product that some gardeners swear by. You may have heard people say you can sprinkle a bit on top of diseased plants or add it to the garden for healthy growth. But is this true?
Although this common white powder is a seemingly benign substance, it’s not always safe for plants. I’ll cover if (and when) this product is safe for plants and provide alternative products that work better in the garden.
The Short Answer
While a little bit of baking soda is unlikely to harm your plants, adding too much of this common home product can cause stress and damage. Although people sometimes claim this white powder is a helpful garden product, you should avoid haphazardly sprinkling it on your plant’s leaves or adding it to beds as a fertilizer. That’s because too much of this product can raise the soil pH above its ideal range and raise salts to an unhealthy level.
With all that said, a small dose of the powder can act as an effective fungicide on diseases including citrus green mold and powdery mildew. However, since sodium bicarbonate tends to crystallize on the surface and become ineffective, other products are more effective against common garden fungi.
The Long Answer
Although you may have heard you can use sodium bicarbonate to control pests, remove fungal diseases, kill weeds, and improve the soil, there’s not much evidence behind these claims. I’ll examine each of these purported claims and explain whether or not they’re true.
What Is It?
You probably know baking soda is a white powder that helps leaven baked goods and remove unpleasant refrigerator odors. But what exactly is this substance? It turns out this powder is a salt known as sodium bicarbonate (NaCHO₃). Other common names include bicarbonate of soda, bread soda, and brewing soda.
This common household product is considered an alkaline substance since its pH is 8.3. Therefore, it can neutralize acidic substances and raise their pH.
Does Baking Soda Kill Pests?
Some people claim you can use this powder to kill garden pests like aphids, caterpillars, and stink bugs. However, there isn’t much evidence to support this claim.
When people suggest using the product to treat pests, they cite one of two main modes of action.
First, they say that the powder will suck the moisture out of soft-bodied pests and therefore kill them. However, it dissolves when it comes into contact with water and isn’t a strong desiccant.
Other individuals claim that the gritty texture of sodium bicarbonate will cut soft-bodied pests. However, the powder is too fine to harm even soft pests like caterpillars and slugs.
Pest Control Alternatives
Fortunately, there are other non-toxic pest control methods. Neem oil and insecticidal soap effectively control a wide range of insect pests. Neem oil slows pest feeding and disrupts hormones, while insecticidal soap suffocates pests. You can also sprinkle diatomaceous earth on and around your plants to deter pests like slugs and snails.
Does Baking Soda Kill Fungi?
Other gardeners claim sodium bicarbonate kills and prevents fungal diseases like powdery mildew, downy mildew, and anthracnose. There is some truth to this claim.
Sodium bicarbonate can slow the growth of fungal diseases, including citrus green mold and powdery mildew. However, the substance often crystallizes on plant leaves and becomes ineffective. Mixing the powder with an emulsifying agent helps limit crystallization and improve the effectiveness.
Even when the powder fails to crystallize, it’s only detrimental to some life stages of the fungi. One study showed that spraying powdery mildew-infected leaves with sodium bicarbonate substantially slowed the germination of spores. However, it didn’t slow the growth of hyphae, the filaments that allow the fungi to spread. When you put these results together, you’ll learn that the powder slows the spread of fungi but doesn’t stop it completely.
Along with considering baking soda’s effectiveness on fungal diseases, you should also assess the potential negative impact of adding this salt to your plants. As salt levels increase, plants experience less leaf growth and lower rates of photosynthesis. Since you have to reapply the powder each time rain or irrigation washes it off your plant, you risk adding too much salt to your garden beds.
Fungicide Alternatives
If you want to avoid fungal diseases, start with cultural practices and variety selection. Installing drip irrigation and maintaining proper plant spacing will help allow for good airflow and keep plant leaves dry, decreasing the odds of fungal diseases occurring. You can also look for disease-resistant varieties of vegetables, fruits, and flowers.
If you spot fungal diseases on your plants, remove and dispose of the infected parts as soon as possible. You can also spray infected plants with a copper solution to slow the spread of disease.
Does Baking Soda Kill Weeds?
Due to its alkaline nature, some people believe that sodium bicarbonate is great for killing weeds. Just mix some of the white powder into water, pour it over the unwanted plants, and watch them shrivel. Unfortunately, this practice isn’t that effective.
While this basic substance can raise soil pH and add salts to make it inhospitable for plants, it won’t kill weeds quickly. If the pH is basic enough to injure weeds, it will also prevent vegetables, flowers, and other desirable plants from growing.
Rather than raising the pH and adding a large amount of salts, consider weed removal methods that harm the weeds without causing long-term damage to the surrounding environment.
Weed Removal Alternatives
There are countless other ways to remove weeds that don’t rely on synthetic herbicides. You can physically remove the plants with your hands, a sharp hoe, or a digging fork. Less physically demanding methods include solarizing the plants with a piece of clear plastic or using an opaque tarp to block the sun and kill the weeds. Flame weeders also work well for killing small weeds.
Does Baking Soda Improve the Soil?
I’ve heard people claim this household substance improves the soil in a way that sweetens tomatoes, encourages plants to produce more flowers, or improves plant growth. But there’s not much science behind these claims.
As I mentioned above, sodium bicarbonate contains just three elements: sodium, carbon, and oxygen. While plants need some sodium to remain healthy, this nutrient is generally not a limiting factor in plant growth. Baking soda can also help raise the pH, which is helpful if you’re dealing with acidic soil. However, adding the powder won’t help your plants if your pH is already near ideal. It could even harm them if the pH is already too alkaline.
Amendment Alternatives
A better way to improve the soil is to add biologically rich compost. This will add beneficial microbes to the soil that help with plant nutrient uptake, disease resistance, and more. Compost also adds organic material that improves soil structure, water infiltration, and moisture retention.
You can also add fertilizers to the soil to ensure your plants can access every nutrient they need. If you’re unsure which nutrients your soil lacks, conduct a soil test before adding any fertilizer.
Key Takeaways
This is not a reliable garden amendment. Science does not back most of the claims made about it, and there are many better options for controlling pest, diseases, and weeds.